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|Title:||Electron Transfer in Mixed-Valence Binuclear Ferrocenes|
|Author(s):||Moore, Michael Francis|
|Department / Program:||Chemistry|
|Degree Granting Institution:||University of Illinois at Urbana-Champaign|
|Abstract:||A single quadrupole-splint doublet is seen in the 4.5 K Mossbauer spectrum for the triiodide salt of 3-acetylbis-(fulvalene)diiron(1+). An IT band at 7140 cm('-1) (e = 1740 M('-1) cm('-1)) is evident in the electronic absorption spectrum. A relatively isotropic EPR signal and a C-H bending band at 840 cm('-1) in the IR spectrum also indicate a delocalized electronic structure.
The x-ray structure of 1,12-dimethyl 1.1 ferrocenophanium triiodide (1) has been determined. One metallocene unit in the binuclear cation has the dimensions expected for an Fe(II) metallocene, whereas the other is an Fe(III) metallocene. Variable-temperature ('57)Mossbauer and magnetic susceptibility and EPR and IR data also indicate that the mixed-valence cation is valence-localized. The triiodide salt of the dication of 1,12-dimethyl 1.1 ferrocenophane has a very weak ((VBAR)J(VBAR) < 0.5 cm('-1)) magnetic exchange interaction between the two S = 1/2 Fe(III) ions.
A single quadrupole-split doublet was observed in the room temperature Mossbauer spectrum for the triiodide salt of 1,6-diethylbiferrocene (2). Two quadrupole-split doublets are seen below 190 K indicating a valence-localized cation. Mossbauer spectra collected for 2 exhibit a constant line width over the temperature range studied. A dynamic disorder model is proposed in which structural changes within the crystal lattice lead to the existence of both localized and delocalized cations. This dynamic disorder occurs at a rate faster than the Mossbauer timescale. Plots of the natural logarithm of the Mossbauer spectral area versus temperature are consistent with this model. Variable-temperature EPR and IR data are presented.
Iodine reacts with 1,12-dione 1.1 ferrocenophane to yield a salt best formulated as 1,12-dione 1.1 ferrocenophane ('2+)(.)(I(,3)('-))(,2)(.)(I(,2))(,2) (3). Resonance Raman data collected on 3 establish the nature of the iodine present in this salt to be of the form (I(,3)('-))(.)(I(,2)). Analytical data show the ratio of Fe/I in 3 is 1:1. These observations suggest that one in five iron atoms in 3 is an Fe(III) ion. Variable-temperature Magnetic susceptibility data and Mossbauer data are consistent with the partial oxidation of 3. The pressed pellet electrical conductivity of 3 is "metal-like" in that increasing conductivity is observed with decreasing temperature.
Thesis (Ph.D.)--University of Illinois at Urbana-Champaign, 1985.
|Date Available in IDEALS:||2014-12-15|